[note from Secessus – this page is updated as I find verifiable information. Problems listed (or not listed) below do not mean one is better than the other. I may have researched some more than others so far. Truly, I don't care what van you buy and live in. It's your home, not mine.]
Everybody thinks their pet van is the best, and that all others will drain your wallet and/or leave you to die a gruesome death on the side of the road. As has been observed in a different context:
That is the way of us chili men. Each of us knows that his chili is light years beyond other chili in quality and singularity; each of us knows that all other chili is such vile slop that a coyote would turn his back on it.1)
In actuality, all vans have issues. The challenge is to find a van that meets your needs, not to find some mythically perfect unicorn that was designed directly by god, never breaks, never needs maintenance and runs forever on one tank of gas and one crankcase of oil. It's like dating: find a van whose weirdnesses don't bother you, and that you can personally live with.
Only a small percentage of failures occur on any particular vehicles; it's not like “this is guaranteed to happen to you!” It's more a list of things to look for, to be aware of. Forums and complaint sites list tons of problems because people with problems are more likely to post. It is rare to see a post saying “drove my van for a year and nothing happened!”. Beware of people who claim “the [fill in the blank] forum is full of unhappy owners!!!” without mentioning unhappy owners of their vans on their forums. Forum links are included below for further research. More popular vans are also more likely to have documented problems, as the ownership base of people who are passionate enough about the vehicles to actually post to ownership forums and meticulously document everything is larger as well.
With that being said, use extreme caution with modern Diesel engines. Tightening emissions requirements have lead to extremely predictable (and expensive) repairs.
Timely maintenance is likely to prevent or lessen the impact of the issues listed below. If your van has recalls or TSBs, try to have it fixed under warranty while it's still free.
1A auto has a video series about the Top 5 problems with many popular vehicles. Select “show all” and scroll down to see if your vehicle is listed.
The Astro/Safari have a cult following due to their mid-size and available AWD.
Learn about this van on the Astro/Safari forum
Transmissions are regarded as generally good, with lifespans like 120,000-180,000 miles on the 4-spd auto 4L80E and 130,000-200,000 miles for the 6-spd 6L90.7)
Learn more about these vehicles on the Express/Savanna subforum.
Made from 1971 - 2003, and hardly changed in the interim. This can be a good thing, as known issues are stable over time. It can be a bad thing in that deficiencies are not addressed over time.
Caravans may be available cheaper than T&C as they generally had fewer options (and less stuff to break).
Learn more about these vehicle on the Chrysler minivan forum.
Models with Stow and Go may have the spare tire mounted in a non-standard position.
Generally very reliable, and 250,000+ miles can reasonably be expected without any major repairs. Relatively easy to work on and fix for the few things that do break. The exception being the diesel engines, however this problem is not limited to Ford.
Common problems on Ford engines not installed in vans, but might be in RVs and Trucks. (All gasoline van engines are 2-valve, not 3-valve).
Achilles heel: transmissions.
Learn more about these vehicles on the Odyssey Club forum.
Autel MD802 code readers are often recommended for those that do their own maintenance.
In general, the (before 2010) T1N models are simpler and often preferred for field maintainability.
Possible workaround: blow out with air, reset code.37)
The NV200 is rated as the most reliable cargo van (any size).41)
Learn more about this vehicle on the NV Forum.
The most reliable van with lowest upfront cost, longest warranty, and lowest annual repair costs outside warranty appears to be the full-size Nissan NV or its minicargo sibling NV200.
Since only a tiny minority of 'dwellers own those vans we can deduce that absolute reliability is not the driving factor in our van-buying decision, no matter what we say.
The cheapest vandwelling solution in terms of purchase price and yearly maintenance appears to be a used Dodge Caravan.57) They are cheap on the used market and even though they are not paradigms of reliability they do have low repair costs. The Town & Country variant is fancier so costs more and has more options to break.
Since only a tiny minority of 'dwellers own those vans we can deduce that absolute cost is not the driving factor in our van-buying decision, no matter what we say.